HP Spectre x2, 12.0", 830gmWeight for tablet only. 1220grms with keyboard.
Unlike the Surface Pro the slim keyboard is included in the box.
HP suggest 10 hours battery life.
Data plan needs investigating for the LTE/4G option. (UK - on EE I can get a 90 day 6G SIM for around 15GBP).
Pen based on N-trig tech.

HP EliteBook Folio 1020 G1, 12.5", 1210gmThere are many options to choose from such as WiFi AC, optional NFC, a QHD screen (2560x1440 piels), up to 512GB SSD, Intel Core M-5Y71 processor and various operating systems. Touch and non-touch versions available. VPro version also available. A Special Edition version cuts 200 grams from the weight with a magnesium chassis. (Total weight 2.2 pounds / 1KG)

HP Pro X2 410 G1, 11.6", 830gmTablet-only weight: 830 grams. With dock: 1596 grams.Also available in Core i3 version and as a consumer focused Pavilion X2 11 with Baytrail and (in some cases) no battery in the keyboard dock.